DE102012016433A1 - Continuous process for the preparation of primary aliphatic amines from aldehydes - Google Patents

Abstract

The present invention relates to a continuous process for the preparation of primary aliphatic amines having 3 to 18 carbon atoms in the molecule by reductive amination of the corresponding aliphatic aldehydes. The reaction is carried out without solvent, the feed aldehyde being reacted with hydrogen and ammonia in the presence of a hydrogenation catalyst above the critical point of ammonia and more than 16 mol ammonia being used per mole feed aldehyde.

Description

The present invention relates to a continuous process for the preparation of primary aliphatic amines having 3 to 18 carbon atoms by reductive amination of the corresponding aliphatic aldehyde with ammonia in the presence of a hydrogenation catalyst above the critical point of ammonia.

Aliphatic amines are important organic intermediates that are produced on a large industrial scale. For example, they are further processed for the production of agrochemicals or dyes or they serve as an additive in surface-active formulations, as a corrosion inhibitor in lubricants or as auxiliaries for the paper, textile and rubber industries.

It is known to produce primary aliphatic amines from aldehydes and ammonia with hydrogen over a catalyst. This reaction is also called reductive amination. The amine formation can be described by the following reaction steps: RC (= O) H + NH ₃ → RC (= NH) H + H ₂ O (1) RC (= NH) H + H ₂ → R-CH ₂ -NH ₂ (2)

In the first reaction stage, an imine is first formed with elimination of water, which is then catalytically hydrogenated in a second reaction stage.

In the reaction, however, occur undesirable side reactions. On the one hand, direct hydrogenation of the feed aldehydes can lead to alcohol formation. Also, the feedstock aldehyde in the basic medium may undergo aldol condensation, and already formed primary amine may react with the feedstock aldehyde via the azomethine intermediate to form a secondary amine which may then further react analogously to a tertiary amine. The aldol condensation products also contain reactive groups which can form higher-boiling condensation products with the nitrogen-containing compounds. In order to improve the selectivity toward the primary aliphatic amines and to suppress the formation of high-boiling by-products, the prior art proposes various measures, for example the use of an excess of ammonia or a solvent, if it is expected that the reaction mixture formed by the Water becomes inhomogeneous ( Houben-Weyl, Methods of Organic Chemistry, 4th Edition, Georg Thieme Verlag Stuttgart, Bd XI / 1, page 602 et seq .).

DE 936 211 describes a liquid phase process for preparing primary aliphatic amines. In this case, the aldehyde to be reacted is first mixed with ammonia at temperatures below 0 ° C. Optionally, the aldehydes are diluted with a low boiling alcohol, for example, methanol. Subsequently, this mixture is catalytically hydrogenated at elevated temperature and elevated pressure in the bottom or trickle mode, for example on a cobalt or nickel contact.

To DE 199 35 448 A1 a mixture of methanol and ammonia with Raney nickel is added and heated after exposure to hydrogen to reaction temperature. Subsequently, the aldehyde is added.

After completion of the reaction, the batch is depressurized, whereby methanol and ammonia evaporate. Subsequently, the remaining primary aliphatic amine is further reacted.

Out DE 10 2010 045 142 A1 is a solvent-free process in the liquid phase is known, in which the feed aldehyde with hydrogen and ammonia in the presence of a hydrogenation catalyst at a temperature of 100 to 170 ° C and at a pressure of 6 to 11 MPa is reacted and wherein per mole of starting aldehyde at least 30th Mol are used ammonia.

The prior art also suggests using ammonia in supercritical conditions in the reductive amination process. The critical temperature of ammonia is 132.5 ° C and the critical pressure is 112.5 atm ( Handbook of Chemistry and Physics, 50th Edition 1969, The Chemical Rubben CO, page F-64 ), corresponding to 11.4 MPa. To GB 1,421,278 the reaction temperature is limited to 160 ° C and the excess pressure to 125 atm (corresponding to 12.7 MPa). In a preferred embodiment, the molar ratio of ammonia to startingaldehyde is limited to 16 to 1. The Embodiment 4 of GB 1,421,278 discloses the reductive amination of isobutyraldehyde with ammonia at a reaction temperature of 140 ° C and at a pressure of 125 atm (12.7 MPa gauge).

According to WO 97/38955 A1 For example, the reductive amination of aldehydes is conducted in a continuous process in the presence of a heterogeneous catalyst with at least one reactant, in addition to hydrogen, in the supercritical state or near the supercritical state. Preferably, the reaction is carried out in the presence of a solvent which under the reaction conditions itself is in the supercritical state, so that hydrogen and the other reaction components are present in a homogeneous phase.

It can not generally be deduced from the prior art that aliphatic aldehydes having an average carbon number at conditions above the critical conditions for ammonia are converted with high selectivity into primary aliphatic amines. Frequently, the formation of high-boiling by-products is observed, which reduce the selectivity and thus the yield of the desired primary aliphatic amine. In addition, the processes according to the prior art tend to have only a limited catalyst lifetime, which in addition to the mentioned reduced yield of the desired amine also associated economic disadvantages for the amination process.

The object of the present invention is therefore to provide a process for preparing primary aliphatic amines which requires little technical effort and with which the desired primary aliphatic amines are obtained with high selectivity. In particular, the formation of high-boiling by-products should be suppressed as much as possible. At the same time, the service life of the hydrogenation catalyst should be extended.

The present invention therefore relates to a continuous process for the preparation of primary aliphatic amines having 3 to 18 carbon atoms by reacting corresponding aliphatic aldehydes with ammonia and hydrogen in the presence of a hydrogenation catalyst. The process is characterized in that the reaction is carried out solvent-free at a molar ratio of aliphatic aldehyde to ammonia of more than 1 to 16 above the critical temperature and above the critical pressure of ammonia.

Surprisingly, in the solvent-free, with respect to ammonia supercritical process control, the formation of selectivity-reducing high boilers can be pressed to less than 10 wt .-% in the reaction product, if the reaction conditions are adjusted specifically in the continuous process control. Another, not to be expected advantage of the method according to the invention lies in the extension of the catalyst life, when ammonia is reacted above its critical point. A separate premixing of the feed ammonia and aliphatic aldehyde with cooling is not required. The starting materials are separated without further equipment measures directly from their templates but simultaneously added to the amination reactor.

The term solvent-free in the context of the present invention is understood to dispense with the active addition of a solvent or diluent. On the other hand, small amounts of secondary constituents in the feedstock, for example production-related alcohol residues in the feedstock aldehydes, may have the solvent or diluent properties. Also, the water formed during the reaction does not fall under the term solvent or diluent, although it acts as a solvent to ammonia.

Per mole of aliphatic aldehyde more than 16 moles of ammonia, preferably at least 18 moles of ammonia and in particular at least 20 moles of ammonia are used. Although the high excess of ammonia leads to a dilution effect and thus counteracts the formation of high boilers, the aldehyde condensation should still proceed to a considerable extent due to the high proportion of the basic reacting compound, especially since no added solvent or diluent is present according to the inventive method. Surprisingly, despite a high ammonia excess, the formation of high-boiling condensation products can be suppressed if the reductive amination is carried out above the critical temperature and above the critical pressure for ammonia. For the achievement of economically viable yields of primary aliphatic amines, it is essential to use more than 16 moles of ammonia per mole of aliphatic aldehyde. An upper limit on the excess of ammonia is not critical and is only determined by procedural or economic considerations. In a preferred embodiment of the invention, the molar ratio of aliphatic aldehyde to ammonia is from 1 to 18 to 1 to 60, preferably from 1 to 20 to 1 to 50.

The reaction of the aliphatic aldehyde with ammonia in the presence of hydrogen on the hydrogenation catalyst is carried out above the critical conditions of ammonia, especially at temperatures above 132.5 ° C to 190 ° C, preferably above 132.5 ° C to 180 ° C and most preferably at temperatures above 160 ° C to 180 ° C. The reaction pressure, the total pressure, is preferably set above 11.4 MPa, the critical pressure of ammonia, up to 20 MPa, in particular above 12.8 to 20 MPa. In particular, a reaction pressure of 13 to 18 MPa is set.

The hydrogenation catalysts used are customary catalysts used in the reductive amination of carbonyl compounds which contain at least one metal from subgroup 8 to 11 of the Periodic Table of the Elements, such as nickel, cobalt, platinum, palladium, iron, rhodium or copper. Particularly preferred are nickel or cobalt catalysts. In addition to carrier-free catalysts, such as Raney nickel or Raney cobalt, supported catalysts can be used. In supported catalysts, the catalytically active metal is generally in an amount of about 5 to 70 wt .-%, preferably about 10 to about 65 wt .-% and in particular about 20 to 60 wt .-%, each based on the total weight of Hydrogenation catalyst before. Suitable catalyst supports are any conventional support materials, for example alumina, alumina hydrates in their various forms, silica, polysilicas (silica gels) including kieselguhr, silica xerogels, magnesia, zinc oxide, zirconia and activated carbon. In addition to the main components of catalytically active metal and support material, the hydrogenation catalysts may also contain additives in minor amounts which serve, for example, to improve their hydrogenation activity and / or their service life and / or their selectivity. Such additives are known, including, for example, the oxides of calcium, barium, zinc, aluminum, zirconium and chromium. They are generally added to the hydrogenation catalyst in a proportion of 0.1 to 30% by weight, based on the total weight of the hydrogenation catalyst. Nickel has proved to be the preferred catalytically active metal. In particular, nickel catalysts on kieselguhr are suitable as carrier material with chromium as additive for the amination process according to the invention. Especially suitable are nickel catalysts containing 20 to 60 wt .-% nickel, 20 to 70 wt .-% diatomaceous earth and 10 to 20 wt .-% of chromium, each based on the total weight of the hydrogenation catalyst and optionally fillers with residue 100% by weight.

The reductive amination is carried out, for example, on fixed catalysts by the trickle or sumping method and in the fluidized bed process. In addition to hydrogen, aliphatic aldehyde and ammonia are separated from the amination reactor but simultaneously fed from their templates.

Preferably, the continuous reductive amination is carried out in a tubular reactor on fixed hydrogenation catalysts. Under a tubular reactor is also a bunch of several closely parallel connected pipes to understand. The tubular reactors used may also contain fillers or internals, for example, Raschig rings, saddles, baffle rings, filter plates or column trays, and optionally stirring devices. In a particularly preferred embodiment, however, the reductive amination takes place in a tubular reactor without internals with a poured hydrogenation catalyst.

In the continuous way, has a catalyst load V / Vh with aliphatic aldehyde, expressed in throughput volume of aliphatic aldehyde per volume of catalyst and time, from 0.02-1.00 h ^-1, preferably 0.10-0.80 h ^-1, proved to be useful. A higher load of the hydrogenation catalyst with aliphatic aldehyde should be avoided, because then the reductive amination is no longer complete and due to the high aldehyde residual content an increased formation of high-boiling by-products is observed.

If the throughputs per unit of time are too low, the system capacity is not optimally utilized.

The reductive amination is carried out in addition to ammonia as the starting compound, preferably with pure hydrogen. In addition to pure hydrogen, however, it is also possible to use mixtures which contain free hydrogen and, in addition, inert constituents under the conditions of the reductive amination.

The aliphatic aldehydes to be reacted by the process according to the invention contain from 3 to 18 carbon atoms in the molecule, preferably from 5 to 15 and more preferably from 8 to 15. The origin of the aliphatic aldehydes is not restricted to specific preparation processes.

Owing to their ready availability, they are obtained by oxo-synthesis or hydroformylation, ie by reaction of the corresponding one-carbon-reduced olefins with carbon monoxide and Hydrogenated aldehydes are preferred, wherein both straight-chain and branched olefins and alicyclic olefins, for example dicyclopentadiene or olefin oligomers such as tripropylene or tetrapropylene, can be used as starting materials for the hydroformylation reaction. Suitable aliphatic aldehydes are both straight-chain n- and branched-chain iso-aldehydes and alicyclic aldehydes either in pure form or as a mixture with isomeric aldehydes of the same carbon number. Mixtures of aliphatic aldehydes of different carbon number can also be used. In particular, aliphatic aldehydes having 8 to 15 carbon atoms can be converted into the corresponding primary aliphatic amines by the procedure according to the invention, for example 2-ethylhexanal, octanal, nonanal, decanal, undecanal, dodecanal, tridecanal, tetradecanal or pentadecanal or mixtures thereof. The corresponding aldehydes can be used as straight-chain compounds, as branched structural isomers or in a mixture of straight-chain and branched structural isomers, even with different carbon numbers. The mixture of straight-chain n- and branched-chain iso-aldehydes which contain 13 and 15 carbon atoms in the molecule is very particularly suitable for the amination process according to the invention. Likewise, according to the procedure of the invention, the preparation of 3 (4), 8 (9) -bis (aminomethyl) -tricyclo [5.2.1.0 ^2,6 ] decane by the reductive amination of 3 (4), 8 (9) - Bis-formyl-tricyclo [5.2.1.0 ^2,6 ] decane.

The reaction mixture removed from the amination reactor is passed into a high-pressure separator, forming a gaseous and liquid phase. The gaseous phase essentially contains ammonia and hydrogen and small amounts of water of reaction and is removed. The resulting liquid phase is expanded by means of a level control to atmospheric pressure and flows into a feed tank. In the expansion process degassed in the liquid phase dissolved ammonia and dissolved hydrogen, which are removed as flash exhaust gas from the storage tank. From the exhaust gas discharged from the high-pressure separator and from the expansion exhaust gas, ammonia can be recovered and returned to the reductive amination process.

From the accumulated in the reservoir liquid phase then residual amounts of ammonia and the water of reaction are removed. The resulting primary aliphatic amine is then purified by processes known per se, for example by distillation, to specification-compliant product.

The catalyst aging effects occasionally observed during continuous operation, which are generally manifested by an increase in the high boiler fraction, can be counteracted by raising the reaction temperature during the ongoing process, for example from above 132.5 ° C to 190 ° C. As a result, the service life of the hydrogenation catalyst can be extended.

By means of the process according to the invention, aliphatic aldehydes can be converted at high conversion into the corresponding primary aliphatic amines with high selectivity. The content of high-boiling by-products, determined by gas chromatography, in the obtained after separation of ammonia and water of reaction formed crude product is less than 10%.

The inventive method is described below with reference to the schematic diagram according to 1 explained in more detail. The inventive method is not limited to the embodiment shown in the drawing.

Over the line ( 1 ) is ammonia, via the line ( 2 ) becomes hydrogen and over the line ( three ) aliphatic aldehyde in the hydrogenation catalyst-filled amination reactor ( 4 ), which is operated above the critical conditions of ammonia. The reactor discharge is via the line ( 5 ) and into a high-pressure separator ( 6 ), in which it comes to the formation of a gaseous and liquid phase. The gas phase from the high-pressure separator ( 6 ) is sent via the line ( 7 ) dissipated. From the discharged gas phase, which consists essentially of ammonia and hydrogen and contains water of reaction in small amounts, ammonia is recovered and again via line ( 1 ) returned to the process (not in 1 shown). The in high-pressure separator ( 6 ) received liquid phase is via the line ( 8th ), via a state regulation ( 9 ) is decompressed to normal pressure and passed over line ( 10 ) without pressure in the storage container ( 11 ) guided. The gaseous fractions formed during the expansion process, essentially residual amounts of dissolved ammonia and hydrogen are passed via the line (FIG. 12 ) discharged. Optionally, ammonia can be recovered from the withdrawn stream and together with fresh ammonia via line ( 1 ) the amination reactor ( 4 ) are returned (not in 1 shown). Via line ( 13 ), the degassed liquid phase is removed and then worked up by distillation methods known per se (not in 1 shown).

In the following, the method according to the invention will be explained in more detail with reference to a few examples.

experimental setup

The reductive amination was carried out on a commercial, kieselgurgeträgerten nickel catalyst with chromium as an additive in a tubular reactor in the upflow mode. As aliphatic aldehyde, a mixture of straight-chain n- and branched-chain iso-C ₁₃ - and C ₁₅ -aldehydes was used. Feed aldehyde, ammonia and hydrogen were separated but fed simultaneously at the bottom of the tubular reactor continuously. The reaction product was taken from the top of the tube reactor and passed into a high-pressure separator. The resulting liquid was decompressed to normal pressure via a level control and fed into a pressureless template. The resulting crude organic product was then analyzed by gas chromatography.

The reaction conditions and the continuous feed of the starting materials were adjusted according to the conditions shown in Tables 1, 2 and 3 below.

The tables also show the gas chromatographically determined composition of the organic product, ammonia-free and anhydrous (in% by volume).

The aliphatic aldehyde mixture used for the experiments in Tables 1-3 had the following typical composition (determined by gas chromatography, data in parts per cent): C ₁₂ and C ₁₄ -KW 2.1 n- / iC ₁₃ aldehyde 62.5 n- / iC ₁₅ aldehyde 34.9 Caster C26-C30 0.5

Comparative Examples 1 and 2 show the results of the reductive amination of an n- / iso-C ₁₃ / C ₁₅ aldehyde mixture under the conditions described in GB 1,421,278 be described as suitable. Striking is the massive high boiler formation when working under the conditions known from the prior art. If, however, according to Inventive Examples 3 and 4, the molar ammonia to aldehyde ratio on the in GB 1,421,278 recommended ratio is increased, the high boiler formation can be reduced to an unexpectedly significant extent.

Comparative Example 5 was carried out according to the conditions of Comparative Example 1, except that the catalyst load was increased to 0.56 h ^-1 , a value also expressed in FIG GB 1,421,278 is detected by area. Compared to Comparative Example 5, in Comparative Example 6, the reaction temperature on the in claim 1 of GB 1,421,278 raised upper limit. Both, in the state of Technique recommended reaction settings observed a significant, economically unacceptable high boiling point formation.

If, according to the reaction settings 7-11 according to the invention, a higher molar ratio of ammonia to aldehyde is used, the high-boiling point formation can be reduced, and the higher the reaction temperature, the clearer it is (Examples 7-10). If, according to Example 11, the pressure is increased from 13 to 16 MPa compared to Example 10, the high-boiling point formation can be reduced again.

The conditions according to the invention are also suitable for compensating aging effects of the fixed-bed catalyst. Example 7 shows the behavior of the hydrogenation catalyst after a running time of 212 h. After a running time of a total of 1708 h (Example 12), a significant increase in high boilers due to the aging of the catalyst is observed. As shown in Examples 13 and 14, the aging effect of the hydrogenation catalyst can be counteracted when the reaction temperature is raised to a range outside of the in GB 1,421,278 recommended temperature range is. By increasing the temperature over the term of the aging effect of the catalyst can be compensated and thus reduces the formation of high boilers and the production of primary C _13/15 amines sustainably operated economically.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 936211 [0006]
• DE 19935448 A1 [0007]
• DE 102010045142 A1 [0009]
• GB 1421278 [0010, 0010, 0038, 0038, 0039, 0039, 0041]
• WO 97/38955 A1 [0011]

Cited non-patent literature

• Houben-Weyl, Methods of Organic Chemistry, 4th Edition, Georg Thieme Verlag Stuttgart, Bd XI / 1, page 602 et seq. [0005]
• Handbook of Chemistry and Physics, 50th Edition 1969, The Chemical Rubben CO, page F-64 [0010]

Claims (13)

A continuous process for the preparation of primary aliphatic amines having 3 to 18 carbon atoms by reacting corresponding aliphatic aldehydes with ammonia and hydrogen in the presence of a hydrogenation catalyst, characterized in that the reaction is solvent-free at a molar ratio of aliphatic aldehyde to ammonia of more than 1 to 16 above the critical temperature and above the critical pressure of ammonia. A method according to claim 1, characterized in that the molar ratio of aliphatic aldehyde to ammonia of 1 to at least 18, preferably from 1 to at least 20. A method according to claim 1 or 2, characterized in that the molar ratio of aliphatic aldehyde to ammonia of 1 to 18 to 1 to 60, in particular from 1 to 20 to 1 to 50, is. Method according to one or more of claims 1 to 3, characterized in that the reaction at a temperature above 132.5 ° C to 190 ° C, in particular above 132.5 ° C to 180 ° C and most preferably above 160 ° C to 180 ° C takes place. Method according to one or more of claims 1 to 4, characterized in that the reaction is carried out at a pressure above 11.4 to 20 MPa, in particular above 12.8 to 20 MPa and most preferably from 13 to 18 MPa. Process according to one or more of claims 1 to 5, characterized in that the aliphatic aldehydes to be reacted contain 5 to 15, preferably 8 to 15, carbon atoms in the molecule. Method according to one or more of claims 1 to 6, characterized in that the hydrogenation catalyst contains at least nickel, cobalt, platinum, palladium, iron, rhodium or copper. Method according to one or more of claims 1 to 7, characterized in that the hydrogenation catalyst contains a carrier material. Method according to one or more of claims 1 to 8, characterized in that the hydrogenation catalyst contains as additives oxides of calcium, barium, zinc, aluminum, zirconium, chromium or mixtures thereof. Process according to one or more of Claims 1 to 9, characterized in that the hydrogenation catalyst used is a nickel catalyst comprising 20 to 60% by weight nickel, from 20 to 70% by weight diatomaceous earth and from 10 to 20% by weight. Contains chromium, in each case based on the total weight of the hydrogenation catalyst and optionally fillers with balance to 100 wt .-%. Process according to one or more of Claims 1 to 10, characterized in that the aliphatic aldehydes to be reacted are used as a mixture of aliphatic aldehydes having a different carbon number. Process according to one or more of claims 1 to 11, characterized in that a mixture of straight-chain n- and branched-chain iso-aldehydes which contain 13 and 15 carbon atoms in the molecule are used. Process according to one or more of claims 1 to 10, characterized in that as aliphatic aldehyde 3 (4), 8 (9) -bis-formyl-tricyclo [5.2.1.0 ^2,6 ] decane is reacted.

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